Presbyopia correction has been a focus of research for the spectacle and contact lens industry for a number of years, with a variety of forms of correction proposed and used commercially. However, many current forms of correction are reliant on some form of visual or convenience compromise, and solutions may not achieve a fully corrected field of vision.
Presbyopia is a natural part of human aging, and is one of the greatest issues facing modern optometry due to demographic shifts in population. Issues arising from presbyopia are difficulties performing near vision tasks such as reading and using a computer. The cause of presbyopia is primarily a reduction in performance of the crystalline lens of the human eye which subsequently results in a corresponding reduction of near vision acuity. In order to address the reduction in focusing power of the crystalline lens in presbyopes, an additional lens with a positive power is required for near vision tasks. However, this correction may result in distance vision being distorted, hence specialist products taking the form of spectacles, contacts lenses or surgery are often required for the correction of presbyopia. The most common correction of presbyopia is the use of reading glasses, which can be removed when desired. For patients with myopia or hyperopia, regular corrective lenses may be worn for distance vision tasks, with reading glasses being used for near vision tasks. However this is not an ideal solution, as spectacles require changing depending on the task performed. In addition to reading glasses, various multifocal and varifocal spectacles exist to provide a range of focusing powers, and can be worn at all times. Recent developments have arisen in the field of spectacle lenses, with electronic liquid crystal lenses commercialised. However, liquid crystal lenses are generally limited by their size, and are hence may be more suited for contact lens correction than spectacle correction. However, contact lens options are more limited due to the inconvenience associated with removing and putting on contact lenses. Alternatively, contact lenses have been designed for correction of presbyopia, where the lens is shaped to give a preferential orientation when worn, leading to different focal lengths and corrective powers depending on the direction of view. Such solutions are found to be highly unsatisfactory for the wearer.